For this study patients with drug resistant tremor (due to PD or essential tremor) are taken to the operating room. While they are awake, an electrode is placed within the ventrointermediate nucleus of the thalamus. Proper placement of this electrode requires physiologic testing whereby various areas of the thalamus are stimulated and the effects are recorded. Once an area can be found that allows adequate tremor suppression with minimal side effects, a permanent stimulator (much like a pacemaker) is implanted just under the skin just below the patient's clavicle. Once the stimulator is in place, the investigator may adjust stimulation parameters to provide the optimal benefit. Post-op evaluation of these patients includes an elaborate examination of their autonomic function within the CRC. In addition to aiding patients with medication-resistant tremor, this study provides us with information regarding various functional areas of the thalamus. In the near future, further studies are planned involving the stimulation of other areas of the basal ganglia for the treatment of other neurodegenerative diseases.